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Author Topic:   New Mercury 90 on a Classic Montauk
erg153 posted 07-30-2014 09:57 AM ET (US)   Profile for erg153   Send Email to erg153  
Does anyone have an opinion on the new Mercury 90 [unclear, probably means to refer to the new Mercury 90-HP engine called the FOURSTROKE, which is based on an entirely new engine block with 2.1-liter displacement] on a classic Montauk with smirked hull? Looks like the dry weight is 359-lbs for the outboard engine, and they seem to get decent reviews from what I've read. Thank you!
jimh posted 07-30-2014 10:30 AM ET (US)     Profile for jimh  Send Email to jimh     
A MONTAUK with a 90-HP outboard engine is a very common configuration, and 90-HP seems like a good match for the hull. Many MONTAUK hulls have been re-powered with 90-HP outboard engines that weigh about 320-lbs, such as the E-TEC 90, and the results have been extremely good.

Increasing the engine weight to 360-lbs from 320-lbs is adding 40-lbs to the transom. Exactly how this will affect the performance is difficult to predict with precision. There has been a notion about engine weight on the MONTAUK hull that suggests that lighter is better, with some experienced owners urging use of smaller and lighter engines, such as 50-HP or 60-HP engines, in order to improve the stability of the hull and reduce a tendency for it to flip over in high winds. See

for a second-hand account of one such incident of flipping over and capsize in high winds with a heavy engine on the transom.

There has been a mixed history of official weight limits for older MONTAUK hulls. An earlier discussion looked into the topic. You may find those comments to have some interest. In general, again, there is trend toward recommendation of less engine weight. See

Maximum Engine Weight

Also, when Boston Whaler was selling the MONTAUK hull in its commercial and government products division (CGP), maximum engine weight rating was 330-lbs. But, then very curiously, they also seemed to once publish for a short time an engine weight maximum for a recreational MONTAUK hull of 410-lbs. This is discussed in .)

One of the best indicators of the transom weight comes by observation of the transom splash well drains. If the transom splash well drains on any Boston Whaler boat are submerged below the water line when the boat is at rest in its static trim, the transom weight is probably greater than was intended by the original designers. This is based on the notion that the original hull designers put the transom splash well drains in a position where they would let water get out of the splash well, not where they would continually allow water to flow into the splash well.

If you have a MONTAUK now with a different engine, perhaps you could add weight to the engine in a temporary manner to bring the engine weight up to the 360-lbs of the Mercury engine. Then you could observe the transom drain position. A 50-lbs sandbag (or two) set carefully atop the engine cowling might do it.

As for the performance of the new Mercury 90 FOURSTROKE based on the new 2.1-liter engine block, I do not recall hearing of anyone report on that in a re-power of a Boston Whaler. I actually have not seen any reports at all about performance of that engine. I expect that owing to the very large 2.1-liter displacement it will certainly be making its rated horsepower.

For many years the Yamaha 90-HP two-stroke engine was considered a top choice for a MONTAUK. That engine had only 1.1-liter of displacement and weighed only 260-lbs. If we use that engine as a benchmark and guide, we see that the new Mercury will have just about twice the displacement and will weigh 100-lbs more.

erg153 posted 07-30-2014 11:28 AM ET (US)     Profile for erg153  Send Email to erg153     
Thanks Jim. A thorough response from you as usual! Yes, I'm referring to Mercury's brand new 90 FOURSTROKE Model 90EL/XLPT. [Note: I assume he means the 90 HP FOURSTROKE based on the 2.1-liter block. Mercury has had three 90-HP FOURSTROKE engines with all the same model names, just different engine blocks. The only way to distinguish them is to mention the block displacement. The 2.1-liter block was just introduced a few weeks ago.--jimh]

My first choice, and seems to be the most popular choice, is the E-TEC 90.

My current setup with regard to the transom is as follows:
Battery at the starboard transom
1990 90hp Mercury (303 lbs)
5hp Mercury kicker on the port transom (maybe 55 lbs)

I float the splash well scuppers with this setup and would be relocating the battery and removing the kicker should I decide to repower. Those two combined should account for the 56 pound difference in main engines. We'll call it 80lbs to make up for prop/oil/etc.

I've read tons of threads and most lean towards the Etec as the preferred option. That being said, I see plenty of Montauks with 4stk 90's hanging off the back so I was curious about Mercury's latest offering.

Thanks again,

Teak Oil posted 07-30-2014 12:45 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
It can be done, Boston Whaler sold the classic hull with 90 4 strokes that weighed 360# back in the day, but I had a Montauk with that much weight on the transom and with a hefty guy in the back it is common to get waves splashing over the transom at rest or when trolling.
jimh posted 07-30-2014 01:04 PM ET (US)     Profile for jimh  Send Email to jimh     
Eric--it sounds like you have about 360-lbs on the MONTAUK transom now with the two engines you have installed already. If you get a new, modern engine, you will find that they can run at idle or trolling speeds very economically, and you probably won't need that auxiliary (kicker) engine for trolling. Unlike the old carburetor two-cycle outboard engines that consumed a lot of extra fuel at idle, modern engines run very efficiently at idle or low speed. Just as an example, my 225-HP modern engine can run at idle for five hours on one gallon.

If you installed the 360-lbs Mercury engine you'd have the same transom weight as you do now. This suggests that it probably won't be a problem--or at least not very different from the boat's present trim and handling.

Moving some weight out of the stern by relocating the engine cranking battery to the console will also help. To do this the best way, try to order the new engine with a set of extra long battery cables. That will give you a nice, one-piece, no-splices or connections, cable run from the console to the engine. The standard length cables may not be long enough. See if you can order longer ones and get a credit or swap on the cost difference.

erg153 posted 07-30-2014 01:26 PM ET (US)     Profile for erg153  Send Email to erg153     
Thanks fellas. Maybe I can be a case study! The decision to re-power has been made; just a matter of when and which brand at this point! I am excited over the options that are available for us these days! Ideally, I would like to wait until the winter and take advantage of some of the deals that can be had during the slower months.
Alan Heckman posted 07-30-2014 01:29 PM ET (US)     Profile for Alan Heckman  Send Email to Alan Heckman     
Repowered this spring. Old set up 2005 Mercury 75 2 stroke and a 9.9 Mercury 2 stroke for a total of 386 LB. New set up Yamaha F70 and Tohatsu 6 HP Sail Pro total weight just under 320 LB. HUGE DIFFERENCE in performance and handling, all for the good. In my experience and opinion too much stern weight is a negative with the 17 FT hull. Put me in the lighter is better group from my personal experience.
erg153 posted 07-30-2014 01:58 PM ET (US)     Profile for erg153  Send Email to erg153     
Thank you Alan. Oddly enough I have a very close childhood friend that shares your last name. We grew up in Delaware together. You can choose not to divulge, but can you give an idea of your total cost (less the kicker)? What all was done when you re-powered? I assume new rigging since you swichted manufacturers. What activities do you do on the boat? Fish/Tube/Cruise?
Alan Heckman posted 07-30-2014 02:42 PM ET (US)     Profile for Alan Heckman  Send Email to Alan Heckman     
Total cost installed, which included a $400 Yamaha rebate was $8725 not including sales tax. This included an analog tach, hour meter, new controls,and a Yamaha Performance Series 13.25 x 14 Stainless Steel Prop. I use my boat for fishing on Lake Erie. This motor gets incredible gas mileage, and as set up tops out about 38 MPH on my 1999 Alert 17.
kwik_wurk posted 08-05-2014 08:55 PM ET (US)     Profile for kwik_wurk  Send Email to kwik_wurk     
Go light. -- If you are going to keep the kicker, Etec 90. If you can part with the kicker, go Merc 90 4S.

I am set up with a merc 90hp (2S) and Merc 4S 6hp (360 total dry), and it is a tad heavy on the kicker side (with electric down riggers and full tanks ~24 gallons).

I compensate by having an over sized anchor and chain, with the heavy down rigger balls in the bow locker. (which averages ~45 lbs) (Battery is in the console.)-- In fact I prefer to strap 94qt cooler on the bow filled with ice versus using the console 94qt cooler.

I am stunned at how the Montauk gets spry, speedy and much better balanced with the kicker (and bracket), and all excess fishing gear (~100lbs) plus down rigger balls removed. Granted the prop torque means a list to port, without the kicker.

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